"Even a small reduction of blood pressure may have important public health benefits and cardiovascular consequences," the researchers wrote, adding that the findings about the "beneficial effect of probiotics on lipid profile suggest that probiotics may be used as a potential supplement for future interventions to prevent hypertension or improve blood pressure control."

Supplement is the key word, since the blood pressure lowering was "minor," commented Nancy K. Sweitzer, MD, PhD, chief of cardiology at the University of Arizona Sarver Heart Center in Tucson, who was not involved in the meta-analysis.

"What I would tell my patients is these compounds are clearly safe," she told MedPage Today. "However, they're expensive to take at this dose for this duration of time."

"The clear message is they should not replace their antihypertensive with yogurt, but that they may get more blood pressure lowering if they add yogurt to their regimen," Sweitzer added. "And that would be great; I always like their blood pressure lower."

"The role of diet in the control of blood pressure is important," noted Merle Myerson, MD, director of cardiovascular disease prevention at Mount Sinai Roosevelt and St. Luke's in New York City.

"Despite [the meta-analysis's] limitations, the results are useful in suggesting where further research should be directed," said Myerson, who also wasn't involved in the meta-analysis.

That message drew agreement from Andi Shane, MD, MPH, a probiotics researcher and pediatric infectious disease expert at Emory University in Atlanta, who added that probiotics wouldn't be a substitute for lifestyle management either, such as cutting sodium intake, getting more exercise, and losing weight.

"It's difficult to extrapolate a single message from the study, as there was quite a lot of heterogeneity in both the subject population and the product that was used," cautioned Shane, who also wasn't involved in the meta-analysis.

The meta-analysis included nine randomized controlled trials that reported blood pressure effects of probiotic products with live cultures in a total of 543 adults with or without hypertension.

Those populations varied widely, though. Three of the trials included only healthy participants without hypertension, while two enrolled patients with high cholesterol, one was done exclusively in hypertension, one in overweight and obese people, and one in the setting of metabolic syndrome.

The interventions varied substantially as well.

Four studies used yogurt as the probiotic source, while two used fermented and sour milk, one used probiotic supplement capsules, one used probiotic rose-hip drinks, and yet another used probiotic cheese.

Four studies used a single species of probiotic bacteria; the rest used combinations of two or three strains. The total daily dose ranged from 109 to 1012 colony-forming units (CFU). Study durations were 3 to 9 weeks.

Individuals with a baseline blood pressure in the normal range didn't gain "meaningful improvements" in either.

Both systolic and diastolic blood pressure findings showed high heterogeneity (P<0.05). Limiting the findings to only double-blind trials or to individuals who were overweight or obese wiped out the association with systolic blood pressure.

While there wasn't a dose-response relationship between daily probiotics consumed and blood pressure reductions, there was some support for a threshold effect.

Trials intervening with at least 1011 CFU showed significant reductions in both systolic and diastolic blood pressure; whereas those with lower doses didn't yield significant reductions in either measure.

"There are a lot of hypotheses about the biological plausibility of how probiotics might work," Shane noted. "There might be some impact on the renin-angiotensin system and some indirect effects by reducing cholesterol and reducing circulating lipids in the blood and therefore affecting blood pressure."

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